Summary A pro-inflammatory signature accompanied by changes in cellular proteostasis are observed in brain neurodegenerative conditions such as AD and to less extent in the aging brain. However, despite the great advancement towards the understanding of the connection between inflammation, AD development and aging-related pathologies, there are several important aspects, which are still very much under investigated. For example albeit it is appreciate the existence of the lymphatic system, as a brain-to-periphery communication conduit, it is still unknown the role played by the lymph in the inflammatory/degenerative process occurring in the brain parenchyma and in transporting the brain molecular signature to the cervical nodes for immune-surveillance. Another important aspect, yet to be investigated, are the very early changes in endosomal proteostasis and the proteome post-translational modifications, occurring before bona fide AD and aging degenerative changes are observed. Finally, despite the fact that active and passive immunotherapy has been proposed for AD the role of MHCII-restricted immune response to naturally processed TAU, A? and other brain self-antigens is still unknown. As such the trust of this application is to: (i) explore the role played by the lymphatic circulation in transporting the inflammatory/degenerative molecular signature of the brain parenchyma to the draining cervical node (with P1 and Core B) (ii) map the very early changes in the brain proteome, PTM- modifications, endo-lysosomal proteostasis and autophagic machinery (with P1 and Core C) (iii) analyze changes in the MHC II-restricted immune-peptidome, and related T cell responses, during aging and the different phases of AD progression (with P3 and Core B). By using state-of the art quantitative proteomic, associated with a cell biology approach, we will map proteins PTMs at different stages of the aging process and AD development as well as their effect on endo-lysosomal proteostasis and the autophagic machinery. Additionally we will investigate the lymph inflammatory/degenerative signature in young and old mice, as well as, AD mice at different stage of disease. Finally, the MHC II-immunopeptidome, eluted from dendritic cells in the cervical node, will be analyzed by MS/MS to map peptides derived from brain-relevant proteins in aging and at different stages of AD. Tetramer staining, using relevant MHC-II-peptides, will be employed to analyze T cell recognition and address the overall immune responses to brain antigens. Altogether results from this project will provide a progressive snap shot of how the cellular proteome is modified during the early-to-late stages of AD or aging development, how the autophagic machinery is involved in disposing the modified proteome, how these early changes progressively develop into complex aggregates and how the endo-lysosomal system is involved in restoring proteostasis. Additionally, how the lymphatic system function as a conduit to transport the inflammatory/degenerative phenotype associated with AD development to the immune system and conversely how immune cells respond to proteomic changes in aging and during AD progression.